1. Field of the Invention
The present invention relates generally to the field of solid-fuel gas-generating devices for inflatable systems, and particularly to those used in inflatable restraint systems.
2. Background of the Invention
Prior art inflatable systems typically use an initiator (such as an electronic squib) and a booster material (such as boron potassium nitrate) to ignite a surrounding, much larger quantity of gas-generating propellant material (such as sodium azide, potassium nitrate or ammonium nitrate, and binders) formed into wafers, discs, pellets, or granules. The gas-generating propellant serves as the primary means by which sufficient gas is produced to deploy the inflatable system. The initiator, the booster material, and the surrounding gas-generating propellant are typically all confined within a metallic structure or assembly, the whole of which forms the "gas generator" which produces inflating gas for an inflatable component (such as an air bag in a passenger vehicle).
This gas generator assembly typically contains one or more internal chambers or baffles, as well as one or more internal sets of filters, which are designed to: (a) control the burn rate of the propellant and the gas mass flow rate, (b) reduce the temperature of the gases produced by the burning of the gas-generating material, and (c) filter out accelerated particles before the gases pass through vents in the assembly and into the airbag itself.
The gas generator is typically located in a position external to the inflatable component (e.g. an airbag) itself, and is attached to the inflatable component by a conduit through which the generated gases flow into the inflatable component, causing the inflatable component to deploy.
Such prior art systems are disclosed, for example, in U.S. Pat. No. 5,738,374 (a pyrotechnic gas generator for an air bag using an annular charge of a mixture of ammonium perchlorate and sodium nitrate, with a silicone binder); U.S. Pat. No. 5,623,115 (a gas generator including a pyrogen igniter enclosing a unitary grain of ignition material, with a squib located to ignite the unitary grain); U.S. Pat. No. 5,483,896 (a housing for a pyrotechnic inflator which serves as a filter for entrapping contaminants and as a cooler by absorbing heat from the generated gas); U.S. Pat. No. 5,443,286 (a gas generating cartridge surrounded by filtering and cooling screens); U.S. Pat. No. 4,200,615 (a linear ignitor and pyrotechnic material extending longitudinally within an elongated enclosure); U.S. Pat. No. 4,950,458 (a two-stage gas generator, in which each stage includes a combustion chamber with an igniter); and U.S. Pat. No. 4,923,212 (a lightweight pyrotechnic inflator consisting of six component parts, including mechanical parts, a filter, a propellant assembly and an initiator).
Hybrid inflators such as the inflators disclosed in U.S. Pat. No. 5,670,738 (a hybrid inflator using compressed gas together with an initiator and a pyrotechnic gas generator), U.S. Pat. No. 5,660,412 (a hybrid inflator consisting of a pressure vessel containing a main charge of pyrotechnic material and a secondary charge of pyrotechnic material, wherein the secondary charge produces products of combustion that ignite the main charge), U.S. Pat. No. 5,588,676 (a hybrid inflator with a pyrotechnic gas generator and a gas chamber storing pressurized gas), U.S. Pat. No. 5,462,307 (a hybrid air bag inflator with a first chamber containing compressed gas and a second chamber containing an igniter and pyrotechnic material) and U.S. Pat. No. 5,131,680 (an inflator assembly which includes pyrotechnic material and a container of gas under pressure) also use gas generating units that are completely separate from and external to the inflatable component (e.g., the air bag) itself.
Example of inflatable components which the present invention can be used to inflate are described in U.S. Pat. No. 5,282,648 (body and head restraints); U.S. Pat. No. 5,322,322 (side impact head strike protection); U.S. Pat. No. 5,480,181 (side impact head strike protection) and U.S. Pat. No. 5,464,246 (tubular cushions), which are all incorporated herein by reference, as well as automotive air bags and other inflatable products.